Summary of Work: This project includes those endeavors in which the mass spectrometry workgroup collaborates with other groups, both inside and outside the Institute to solve problems of mutual interest. The major focuses of these projects are: 1) structure determination of unknown compounds; 2) identification and/or confirmation of biological pathways; 3) quantitation; and 4) development of strategies for the structure determination of biologically important compounds. Current major collaborative projects under way include: 1)identification of potential ligands of orphan receptors (C. Weinberger, LRDT); 2) quantitation of arachidonic acid metabolites (D. Zeldin, LPP).Quantitation of Arachidonic Acid Metabolites - The most sensitive and accurate method for quantitation of eicosanoids in physiological samples is by selected ion monitoring (SIM) under negative ion chemical ionization (NICI) mass spectrometry. We are currently quantifying eicosanoid metabolites as part of several studies. These include: Characterized the arachidonic acid metabolites of a new cytochrome P450, CYP2J5, isolated from a mouse liver cDNA library and abundantly expressed within tubules of the renal cortex. CYP2J5 arachidonic acid oxidation products are postulated to play important functional roles in the kidney. Characterization of arachidonic acid metabolites in fish including studies on the alteration of endogenous arachidonic acid metabolism in response to environmental toxins such as TCDD and BP. Characterization of the arachidonic acid metabolites of a new cytochrome P450, CYP2J5, isolated from a mouse liver cDNA library and abundantly expressed in kidney whose products are postulated to play important functional roles in the kidney. Characterization of arachidonic acid metabolites in hypertensive vs. non-hypertensive rats.This project includes those endeavors in which the mass spectrometry workgroup collaborates with other groups, both inside and outside the Institute to solve problems of mutual interest. The major focuses of these projects are: 1) structure determination of unknown compounds; 2) identification and/or confirmation of biological pathways; 3) quantitation; and 4) development of strategies for the structure determination of biologically important compounds. Current major collaborative projects under way include: 1)identification of potential ligands of orphan receptors (C. Weinberger, LRDT); 2) quantitation of arachidonic acid metabolites (D. Zeldin, LPP).Quantitation of Arachidonic Acid Metabolites - The most sensitive and accurate method for quantitation of eicosanoids in physiological samples is by selected ion monitoring (SIM) under negative ion chemical ionization (NICI) mass spectrometry. We are currently quantifying eicosanoid metabolites as part of several studies. These include: Characterized the arachidonic acid metabolites of a new cytochrome P450, CYP2J5, isolated from a mouse liver cDNA library and abundantly expressed within tubules of the renal cortex. CYP2J5 arachidonic acid oxidation products are postulated to play important functional roles in the kidney. Characterization of arachidonic acid metabolites in fish including studies on the alteration of endogenous arachidonic acid metabolism in response to environmental toxins such as TCDD and BP. Characterization of the arachidonic acid metabolites of a new cytochrome P450, CYP2J5, isolated from a mouse liver cDNA library and abundantly expressed in kidney whose products are postulated to play important functional roles in the kidney. Characterization of arachidonic acid metabolites in hypertensive vs. non-hypertensive rats. - Gas chromatography/mass spectrometry arachidonic acid epoxygenase